There are gazillions of drum kits to download for very reasonable penny.

You have to download VLib software. This allows you to manipulate the kits. You need a midi interface or a simple midi lead and your are off. You download the kits from vexpressions. Then you set up this:

computer -> midi interface ->midi leads (2 off) -> TD12.

You save all the Roland kits first. Then you play around with VLib and hey presto all your TD12 kits have disappeared and been replaced with new kits.

Now the reason I like the kits so much is because they sound in decent headphones to be really tasty. I won't say accurate, but they really are good quality. I don't use the Roland kits at all.

Hope this encourages you - I'm 49 and I managed it with my TD6 and my TD12 so I'm sure you can do it.